swift234

Updated the PlaygroundTransform to no longer
require that the modules it uses are present.
LLDB now explicitly forward-declares the builtins
that transformed code requires, so we can just
use them.

This makes the playground transform less error
prone, and means that if the functions really are
missing we'll get a nice and obvious link error
rather than a hard-to-diagnose error where the
playground transform quietly refuses to do
anything.

<rdar://problem/16599338>


Swift SVN r16563